Oil pump

ABSTRACT

An oil pump, includes an inner rotor having outer teeth; an outer rotor having inner teeth which form cells together with the outer teeth, the outer rotor rotating with a prescribed amount of eccentricity with respect to the center of rotation of the inner rotor; an outer ring which causes the center of rotation of the outer rotor to swing along a fan-shaped rotation trajectory having a radius equal to the amount of eccentricity, with respect to the center of rotation of the inner rotor; an operating means which causes a swinging movement of the outer ring; and a pump housing which has a rotor chamber having an intake port and a discharge port, the portion between a final end section of the intake port and a start end section of the discharge port being taken to be a first sealing land.

TECHNICAL FIELD

The present invention relates to an oil pump which is installed in a vehicle engine or the like and the discharge amount of which can be varied, and more particularly to an oil pump in which an operation for varying the discharge amount can be carried out smoothly and good pump efficiency can be achieved.

BACKGROUND ART

Conventionally, there have been various oil pumps having a variable discharge amount. Among these, there are oil pumps each provided with an inner rotor, an outer rotor, and movement means for moving the outer rotor along a prescribed trajectory, wherein the discharge amount can be varied by moving the outer rotor via the movement means. Patent Literature 1 discloses a typical example of this.

CITATION LIST Patent Literature [PTL 1]

Japanese Patent Application Publication No. H10-169571

SUMMARY OF INVENTION Technical Problem

In Patent Literature 1, an adjustment ring is used as the movement means for the outer rotor. Outer teeth are formed on the adjustment ring, and a plurality of inner teeth are formed respectively in the circumferential direction on a sheet metal ring in a housing. Therefore, the manufacturing process takes time, and the costs rise.

The object of the present invention (the technical problem to be solved) is to enable smooth movement of the outer rotor along a prescribed trajectory with respect to the inner rotor, and also to achieve same by a very simple configuration.

Solution to Problem

As a result of thorough research in order to resolve the abovementioned problem, the present inventors resolved the abovementioned problem by configuring the invention according to claim 1 as an oil pump including: an inner rotor having outer teeth; an outer rotor having inner teeth which form cells together with the outer teeth, the outer rotor rotating with a prescribed amount of eccentricity with respect to the center of rotation of the inner rotor; an outer ring which causes the center of rotation of the outer rotor to swing along a fan-shaped rotation trajectory having a radius equal to the amount of eccentricity, with respect to the center of rotation of the inner rotor; an operating means which causes a swinging movement of the outer ring; and a pump housing which has a rotor chamber having an intake port and a discharge port, the portion between a final end section of the intake port and a start end section of the discharge port being taken to be a first sealing land, and which houses the inner rotor, the outer rotor and the outer ring, wherein the oil pump is provided with no less than three and no more than eight tooth shape sections, each formed of an outside position tooth shape formed in the rotor chamber and an inside position tooth shape which is formed in the outer ring to form a pair with the outside position tooth shape and which intermeshes therewith at all times while moving, and a prescribed interval is provided between the adjacent tooth shape sections.

The abovementioned problem was also solved by configuring the invention according to claim 2 as the oil pump according to claim 1, wherein the number of tooth shape sections is no less than three and no more than six. The abovementioned problem was also solved by configuring the invention according to claim 3 as the oil pump according to claim 1, wherein the number of tooth shape sections is four or five. The abovementioned problem was also solved by configuring the invention according to claim 4 as the oil pump according to claim 1, wherein the number of tooth shape sections is four.

The abovementioned problem was also solved by configuring the invention according to claim 5 as the oil pump according to any one of claims 1, 2, 3 and 4, wherein an operating protrusion, one side of which in a swinging direction is taken to be a first pressure receiving surface and the other side of which is taken to be a second pressure receiving surface, is formed on an outer circumference of the outer ring, an operating chamber in which the operating protrusion is accommodated swingably is formed adjacently to and in connection with the rotor chamber, a first oil passage for sending oil to the first pressure receiving surface by the operating means and a second oil passage for sending oil to the second pressure receiving surface by the operating means are formed in the operating chamber, and the operating protrusion is configured to swing due to an oil pressure differential between the first oil passage side and the second oil passage side.

Advantageous Effects of Invention

In the invention of claim 1, no less than three and no more than eight tooth shape sections are provided, each comprising an outside position tooth shape formed in the rotor chamber and an inside position tooth shape which is formed in the outer ring to form a pair with the outside position tooth shape, and which intermeshes therewith at all times while moving, and there is a prescribed interval between the adjacent tooth shape sections.

By the configuration described above, since the number of tooth shape sections is reduced and a prescribed interval is provided between the adjacent tooth shape sections, then it is possible to reduce the motive power for causing the outer ring to swing, while being able to cause the outer ring to swing smoothly. Moreover, when the outer rotor, together with the outer ring, is in the initial position and the final position, the inside position tooth shapes and the outside position tooth shapes in the tooth shape sections are in an intermeshed state, and therefore the outer rotor is held satisfactorily in position in the initial position and the final position, and a stable pump operation can be achieved.

By configuring the invention according to claim 2 as the oil pump according to claim 1, wherein the number of tooth shape sections is no less than three and no more than six, the number of tooth shape sections is desirable for causing the outer ring to swing, and in the invention according to claim 3, the number of tooth shape sections is made even more desirable by being set to four or five. In the invention according to claim 4, by setting the number of tooth shape sections to four, an optimal configuration is achieved which has the best balance between the motive power for causing the outer ring to swing, and the holding of the outer ring in the initial position and final position. In the invention according to claim 5, the swinging movement of the outer ring by the operating means is performed by hydraulic pressure, and hence the operation is performed very reliably and a satisfactory swinging movement of the outer ring can be performed.

If a sealing section is provided in at least one of the rotor chamber or the outer ring, the sealing section abutting against the other of the rotor chamber and outer ring and shutting the intake port from the discharge port, then it is possible to prevent the oil present in the small gap between the inner circumference side of the rotor chamber and the outer circumference side of the outer ring from leaking out to the intake port from the discharge port.

Moreover, by configuring the oil pump such that, in the low-speed range of the engine, the outer rotor is in an initial position due to the outer ring and the cell on the first sealing land is largest, and in the medium-speed and high-speed ranges of the engine, the cell is inside the intake port and the cell is largest, then it is possible to adjust increase and decrease in the discharged oil in a very satisfactory manner, from the low-speed range through to the high-speed range of the engine.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1(A) is an enlarged diagram showing a state of contact by tooth shape sections in a rotor chamber and an outer ring according to the present invention, FIG. 1(B) is an enlarged view of part (K1) in (A), FIG. 1(C) is an enlarged view of part (K2) in (A), FIG. 1(D) is an enlarged view of part (K3) in (A), and FIG. 1(E) is an enlarged view of part (K4) in (A);

FIG. 2(A) is an enlarged cross-sectional view showing a state in an initial position of an outer rotor, an inner rotor and an outer ring having four tooth shape sections, according to the present invention, and FIG. 2(B) is an enlarged view of a fan-shaped rotation trajectory;

FIG. 3 is an enlarged cross-sectional view showing a state in an intermediate position of an outer rotor, an inner rotor and an outer ring having four tooth shape sections, according to the present invention;

FIG. 4 is an enlarged cross-sectional view showing a state in a final position of an outer rotor, an inner rotor and an outer ring having four tooth shape sections, according to the present invention;

FIG. 5(A) is a cross-sectional diagram showing a state in an initial position of the outer rotor, the inner rotor and the outer ring having three tooth shape sections, and FIG. 5(B) is a cross-sectional diagram showing a state in the final position of the outer rotor, inner rotor and outer ring having three tooth shape sections;

FIG. 6(A) is a cross-sectional diagram showing a state in an initial position of the outer rotor, the inner rotor and the outer ring having six tooth shape sections, and FIG. 5(B) is a cross-sectional diagram showing a state in the final position of the outer rotor, inner rotor and outer ring having six tooth shape sections;

FIG. 7(A) is a schematic drawing showing a partial cross-section of the present invention; FIG. 7(B) is a principal lateral cross-section plan diagram of a pump housing; FIG. 7(C) is a plan diagram of the outer ring; FIG. 7(D) is an enlarged view of part (K5) in (A); and FIG. 7(E) is a cross-sectional diagram along arrows Y1-Y1 in (D); and

FIG. 8(A) is a graph showing the characteristics of the present invention, and FIGS. 8(B) and 8(C) are principal cross-sectional diagrams showing a state of operation of an operating protrusion.

DESCRIPTION OF EMBODIMENTS

Implementations of this invention are described below with reference to the drawings. The present invention is principally configured by a pump housing A, an inner rotor 3, an outer rotor 4, an outer ring 5 and an operating means 9, as shown in FIGS. 1 to 4 and FIG. 7, etc. A rotor chamber 1 is formed in the pump housing A. A shaft hole 11 into which a drive shaft for driving the pump is fitted is formed in a bottom surface section 1 a of the rotor chamber 1, and an intake port 12 and a discharge port 13 are formed in the periphery of the shaft hole 11. Furthermore, a sealing land is formed between the intake port 12 and the discharge port 13.

The sealing land is formed at two positions inside the rotor chamber 1, one of which is situated between a final end portion 12 b of the intake port 12 and a start end portion 13 a of the discharge port 13, this sealing land being called the first sealing land 14 (see FIG. 2 to FIG. 4 and FIG. 7(B), etc.)

Furthermore, the other sealing land is situated between the final end portion 13 b of the discharge 13 and the start end portion 12 a of the intake port 12, and this sealing land is called a second sealing land 15 (see FIG. 2 and FIG. 3, FIG. 7(B) and the like). An operating chamber 2 that is connected to the rotor chamber 1 is formed in the pump housing A, and an operating protrusion 51 of the outer ring 5, which is described below, is disposed therein. The inner rotor 3, the outer rotor 4 and the outer ring 5 are installed inside the rotor chamber 1 (see FIG. 2 to FIG. 4, etc.)

The inner rotor 3 is a gear wheel having a trochoid shape or substantial trochoid shape, on which a plurality of outer teeth 31, 31, . . . are formed (see FIG. 2 to FIG. 4). Furthermore, a boss hole 32 for the drive shaft is formed in a central position thereof in the radial direction, and the drive shaft 33 is passed through and fixed in the boss hole 32. The boss hole 32 is formed in a non-circular shape, and the drive shaft 33 is fixed to the inner rotor 3 by a fixing means such as pressure-fitting or a two-face width part, etc. in a shaft fixing portion having substantially the same shape as the boss hole 32, whereby the inner rotor 3 turns with the rotational driving of the drive shaft 33.

The outer rotor 4 is formed in a ring shape, and a plurality of inner teeth 41, 41, . . . are formed in the inner circumferential side thereof. The number of outer teeth 31 on the inner rotor 3 is one fewer than the number of inner teeth 41 on the outer rotor 4. A plurality of cells (spaces between teeth) S, S, . . . are formed by the outer teeth 31, 31, . . . on the inner rotor 3, and the inner teeth 41, 41, . . . on the outer rotor 4.

The center of rotation of the inner rotor 3 is called Pa. This center of rotation Pa is immobile in relation to the rotor chamber 1. The center of rotation of the outer rotor 4 is called Pb. The virtual line linking the center of rotation Pa and the center of rotation Pb is called the eccentric axis line. The eccentric axis line includes an initial position eccentric axis line La and a final position eccentric axis line Lx, in accordance with the initial positions of the outer rotor 4 and the outer ring 5 (see FIG. 2(B)).

The distance between the center of rotation Pa of the inner rotor 3 and the center of rotation Pb of the outer rotor 4 is called an amount of eccentricity e. A trajectory circle centered on the center of rotation Pa of the inner rotor 3 and having a radius equal to the amount of eccentricity e is created. By the operation of the outer ring 5, the center of rotation Pb of the outer rotor 4 moves along a fan-shaped circular arc which is one portion of the trajectory circle, from an initial position state to a final position state. The circular arc-shaped trajectory portion of the center of rotation Pb in this case is called the fan-shaped rotational trajectory Q (see FIG. 2, FIG. 3, FIG. 4, etc.)

The outer ring 5 is formed in a substantial circular ring shape, and an operating protrusion 51 formed in a protruding shape is provided in the outward radial direction from a prescribed position on the outer circumference side surface 5 a thereof (see FIG. 7(C)). Furthermore, a gripping section 52 which is a perfectly circular through hole is formed in the inner side of the outer ring 5. The outer ring is caused to swing inside the rotor chamber 1 by the operating means 9 (described below) via the operating protrusion 51. The operating protrusion 51 is disposed in the operating chamber 2 and can swing inside the operating chamber 2.

The gripping section 52 is formed on a circular inner circumference wall surface, and the inner diameter of the gripping section 52 is the same as the outer diameter of the outer rotor 4. In practice, the inner diameter of the gripping section 52 is slightly larger than the outer diameter of the outer rotor 4, and the outer rotor 4 is inserted with a clearance between the gripping section 52 and the outer rotor so that the outer rotor 4 can rotate smoothly, but this configuration is included in the concept of “same”.

A center of the diameter Pc of the gripping section 52 of the outer ring 5 coincides with the center of rotation Pb of the outer rotor 4 in a state of being inserted into the gripping section 52 (see FIG. 2 to FIG. 4). The outer ring 5 is disposed inside the rotor chamber 1, the outer rotor 4 being disposed inside the gripping section 52 such that the outer rotor 4 is supported rotatably and is also caused to swing along the fan-shaped rotation trajectory Q via the operating means 9 described below.

The outer ring 5 is installed inside the rotor chamber 1 of the pump housing A, and is configured swingably within the rotor chamber 1. Therefore, the rotor chamber 1 is formed to be slightly broader than the outer shape of the outer ring 5, and a space permitting the outer rotor 4 to swing is provided. The outer ring 5 is caused to perform a swinging movement by the operating means 9, but the trajectory of this swinging movement is fixed, and the center of diameter Pc of the gripping section 52 swings along this fan-shaped rotation trajectory Q (see FIG. 2 to FIG. 4).

A first pressure receiving surface 51 a is formed on the operating protrusion 51 on one surface side in the direction of the swinging movement and a second pressure receiving surface 51 b is formed thereon on the other surface side. A first oil passage 21 is formed in a first side wall surface 2 a of the operating chamber 2, which opposes the first pressure receiving surface 51 a of the operating protrusion 51, and a second oil passage 22 is formed in a second side wall surface 2 b which opposes the second pressure receiving surface 51 b.

Moreover, an elastic pressing section 8 is provided on the side of the second side wall surface 2 b. The elastic pressing section 8 is configured by an elastic section 81 and a pressing head section 82. The elastic section 81 is, more specifically, a coil spring, and the pressing head section 82 is a substantially hemispherical cap member. Furthermore, a cylindrical hole-shaped elastic section accommodating chamber is formed in the second side wall surface 2 b, and the elastic section 81 and the pressing head section 82 are accommodated in the elastic section accommodating chamber 83. The pressing head section 82 of the elastic pressure section 8 abuts against the second pressure receiving surface 51 b of the operating protrusion 51, and the outer ring 5 is impelled elastically towards the first side wall surface 2 a, so as to be held in an initial position (see FIG. 2 to FIG. 4 and FIG. 7(B), etc.)

An operating means 9 which sends oil into the operating chamber 2 via the first oil passage 21 and the second oil passage 22 is provided on the outside of the pump housing A. The operating means 9 is, more specifically, a hydraulically-controlled valve, and causes the operating protrusion 51 of the outer ring 5 to swing due to hydraulic pressure (see FIG. 7(A)).

The oil sent out into the operation chamber 2 from the first oil passage 21 applies a force by pressure to the first pressure receiving surface 51 a of the operating protrusion 51. The oil sent out into the operation chamber 2 from the second oil passage 22 applies a force by pressure to the second pressure receiving surface 51 b of the operating protrusion 51. The operating protrusion 51 swings due to the pressure differential applied to the first pressure receiving surface 51 a and the second pressure receiving surface 51 b, and the elastic pressing force of the elastic pressing section 8.

A seal section 7 is provided on at least either one of the rotor chamber 1 (including the operating chamber 2) or the outer ring, abuts against the other thereof, and thereby shuts off the intake port 12 from the discharge port 13. More specifically, the seal section 7 is provided on either one of the inner circumference side surface 1 b of the rotor chamber 1 or the outer circumference side surface 5 a or operating protrusion 51 of the outer ring 5, and abuts against the outer circumference side surface 5 a or the inner circumference side surface 1 b on the other side thereof. Therefore, oil flows through the gap occurring between the inner circumference side surface 1 b of the rotor chamber 1 and the outer circumference side surface 5 a of the outer ring 5, but the oil is prevented from flowing in reverse from the discharge port 13 to the intake port 12.

The seal section 7 includes a seal head section 71 and a seal elastic section 72 (see FIG. 2 to FIG. 4, FIGS. 7A, 7D and 7E, etc.) If the seal section 7 is provided on the inner circumference side surface 1 b of the rotor chamber 1, then a small seal chamber 73 is formed on the inner circumference side surface 1 b of the rotor chamber 1, and the seal head section 71 and the seal elastic section 72 are accommodated in the small seal chamber 73. A small expulsion hole 73 a is formed in the small seal chamber 73, and is communicated with the inside of the rotor chamber 1. Inside the small seal chamber 73, the seal head section 71 is impelled elastically so as to project externally by the seal elastic section 72.

The tip of the seal head section 71 abuts against and elastically presses the outer circumference side surface 5 a of the outer ring 5 or an inside position tooth shape 6 a. The seal head section 71 contacts the whole of the outer ring 5 in the thickness direction, and shuts off the gap between the inner circumference-side surface 1 b of the rotor chamber 1 and the outer circumference-side surface 5 a of the outer ring 5. Furthermore, if the seal section 7 is provided on the side of the outer ring 5, then the small seal chamber 73 is formed in the operating protrusion 51 of the outer ring 5, and the seal head section 71 and the seal elastic section 72 are accommodated in the small seal chamber 73. If the seal section 7 is provided in the operating protrusion 51, the seal head section 71 abuts against the apex-side wall surface 2 c of the operating chamber 2.

Consequently, it is possible to prevent reverse flow of oil from the discharge port 13 to the intake port 12 via the gap. Furthermore, the small expulsion hole 73 a formed in the small seal chamber 73 serves to expel the oil that has flowed into the small seal chamber 73, into the rotor chamber 1, when the seal head section 71 is pressed into the small seal chamber 73.

Here, the small expulsion hole 73 a serves as an orifice, when expelling oil, and serves as a damper, when the seal head section 71 is pushed back into the small seal chamber 73. The seal section 7 is provided at the position of the operating protrusion 51 of the outer ring 5. Firstly, the small seal chamber 73 is formed at the position of the apex section 51 c of the operating protrusion 51, the seal elastic section 72 and the seal head section 71 are accommodated inside the small seal chamber 73, and the seal head section 71 contacts the apex-side wall surface 2 c of the operating chamber 2 at all times.

The operating chamber 2 is separated in liquid-tight fashion by the operating protrusion 51, and the control of hydraulic pressure of the operating protrusion 51 by the operating means 9 can be performed reliably, without interchanging of the oil flowing in from the first oil passage 21 and the second oil passage 22. Furthermore, the oil is prevented from flowing out to the intake port 12 or the discharge port 13 via the operating chamber 2.

In the present invention, the inner rotor 3 and the outer rotor 4 have an initial position and a final position, and as shown in FIG. 2, the initial position means the position of the inner rotor 3, the outer rotor 4 and the outer ring 5 when the largest cell Sa having the largest volume of the plurality of cells S, S, . . . formed by the inner rotor 3 and the outer rotor 4 is situated on the first sealing land 14. Furthermore, in this initial position, the number of revolutions of the engine is mainly in a low-speed range. The eccentric axis line linking the center of rotation Pa of the inner rotor 3 and the center of rotation Pb of the outer rotor in this initial position is called the initial position eccentric axis line La (see FIG. 2).

Furthermore, as shown in FIG. 4, the final position is the position of the outer ring 5, the inner rotor 3 and the outer rotor 4 when the outer ring 5 has swung to a maximum extent from the initial position, the center of rotation Pb of the outer rotor 4 has moved along the fan-shaped rotation trajectory Q and the position of the largest cell Sa has moved to a maximum extent. In this case, the revolutions of the engine are in a medium and high-speed range. The eccentric axis line linking the center of rotation Pa of the inner rotor 3 and the center of rotation Pb of the outer rotor 4 in this final position is called the final position eccentric axis line Lx (see FIG. 4).

If θ is taken to be the angle through which the outer rotor 4 swings in practice due to the outer ring 5, from the initial position eccentric axis line La to the final position eccentric axis line Lx, and θ1 is taken to be the angle through which the operating protrusion 51 of the outer ring 5 swings in this case, then the angle θ1 is markedly smaller than the angle θ.

In other words, while the outer ring 5 only causes the operating protrusion 51 to swing through a small angle of θ1 by the operating means, the maximum swing angle of the outer rotor 4, in other words, the angle θ formed between the initial position eccentric axis line La and the final position eccentric axis line Lx can be made very large indeed. More specifically, while the swing angle of the operating protrusion 51 is approximately 15 degrees, the angle formed between the initial position eccentric axis line La of the outer rotor 4 and the final position eccentric axis line Lx can be set to approximately 120 degrees (see FIG. 2 to FIG. 4).

Next, the tooth shape sections 6 are described. The tooth shape sections 6 are formed respectively in the rotor chamber 1 and the outer ring 5, and serve as a guide in such a manner that, when the outer ring 5 swings, the center of diameter Pc of the outer ring 5 can accurately move reciprocally along the set fan-shaped rotation trajectory Q (see FIG. 1 to FIG. 4, etc.) In other words, the center of diameter Pc of the gripping section 52 of the outer ring 5 is guided so as to be able to swing along the fan-shaped rotation trajectory Q, while the center of rotation Pb of the outer rotor 4 maintains the amount of eccentricity e with respect to the center of rotation Pa of the inner rotor 3.

The tooth shape sections 6 are provided between the outer ring 5 and the rotor chamber 1, and are each configured from an inside position tooth shape 6 a and an outside position tooth shape 6 b. The inside position tooth shape 6 a is formed on the outer circumference-side surface 5 a of the outer ring 5. The outside position tooth shape 6 b is formed on the inner circumference-side surface 1 b of the rotor chamber 1 (see FIG. 1). One tooth shape section 6 is configured by a pair consisting of an inside position tooth shape 6 a and an outside position tooth shape 6 b, and a plurality of the tooth shape sections 6 is provided on the outer ring 5 and the rotor chamber 1.

Furthermore, in the plurality of tooth shape sections 6, 6, . . . , there is a prescribed interval between the adjacent tooth shape sections 6, 6. In other words, the plurality of tooth shape sections 6, 6, . . . are discontinuous rather than being continuous in the manner of a gear wheel. Moreover, the intervals between the tooth shape sections 6, 6, . . . are not uniform (see FIG. 1, FIGS. 7B, 7C and the like). Furthermore, the intervals between the tooth shape sections 6, 6, . . . may also be uniform.

The inside position tooth shapes 6 a and the outside position tooth shapes 6 b are intermeshed at all times, and the inside position tooth shapes 6 a move while making smooth contact with the outside position tooth shapes 6 b. The inside position tooth shapes 6 a and the outside position tooth shapes 6 b have arc-shaped teeth. The inside position tooth shapes 6 a and the outside position tooth shapes 6 b are each formed by an individual arc-shaped line, or are formed by smoothly linking a plurality of different arc-shaped lines.

More specifically, the inside position tooth shapes 6 a and the outside position tooth shapes 6 b are formed in a protruding shape or recessed shape by arc-shaped lines, or by smoothly connecting protrusions and recesses. Furthermore, the tooth shape sections 6 are configured such that, more specifically, the inside position tooth shapes 6 a have an arc-shaped tooth shape which is a modified trochoid shape, and the outside position tooth shapes 6 b have an arc-shaped tooth shape which is a modified circular shape.

However, the inside position tooth shapes 6 a and the outside position tooth shapes 6 b of the tooth shape sections 6 are not limited to the tooth shapes described above and may have an arc shape based on any definition, provided that the inside position tooth shapes 6 a and the outside position tooth shapes 6 b are guided so as to intermesh smoothly while making contact with each other at all times, in the course of the outer ring 5 moving from the initial position to the final position.

A pair formed by an inside position tooth shape 6 a and an outside position tooth shape 6 b never intermeshes with the inside position tooth shape 6 a or outside position tooth shape 6 b of another pair. In other words, a configuration is adopted in which only the inside position tooth shape 6 a and the outside position tooth shape 6 b forming the same pair intermesh with each other. Furthermore, a state where an inside position tooth shape 6 a and an outside position tooth shape 6 b forming a pair are intermeshed is a state that permits smooth relative movement thereof in a state of mutual contact.

The range of intermeshing of the inside position tooth shapes 6 a and the outside position tooth shapes 6 b, in other words, the portion in which the respective tooth shapes contact each other and can slide relative to each other while the contact portion thereof changes, is different in each of the tooth shape sections 6, and can vary from a relatively broad range to a relatively narrow range. In FIGS. 1B, 1C, 1D and 1E, in the respective tooth shape sections 6, 6, . . . , a contact region 6 t is indicated in which the inside position tooth shape 6 a and the outside position tooth shape 6 b slide in contact with each other.

In the course of the outer ring 5 moving the outer rotor 4 from the initial position to the final position by the plurality of tooth shape sections 6, 6, . . . , the center of diameter Pc of the outer ring 5 and the center of rotation Pb of the outer rotor 4 are guided so as to move along the fan-shaped rotation trajectory Q. Furthermore, during the course of this movement, the inside position tooth shape 6 a and the outside position tooth shape 6 b forming a pair in each of the tooth shape sections 6 are in contact with other at all times.

The formation positions of the plurality of outside position tooth shapes 6 b, 6 b, . . . in the rotor chamber 1 are on the inner circumference-side surface 1 b in a range between the intake port 12 and the discharge port 13 (see FIG. 1 and FIG. 7B). The gap occurring between the inner circumference-side surface 1 b of the rotor chamber 1 and the outer circumference-side surface 5 a of the outer ring 5 is sealed in a liquid-tight fashion by the intermeshing and mutual contact between the outside position tooth shapes 6 b and the inside position tooth shapes 6 a that respectively form pairs therewith.

Consequently, the connected state between the intake port 12 and the discharge port 13 via the gap is shut off, thereby setting same to a non-connected state. In other words, the gap formed between the outer circumference-side surface 5 a of the outer ring 5 and the inner circumference-side surface 1 b of the rotor chamber 1 is shut off by the contact between the inside position tooth shapes 6 a and the outside position tooth shapes 6 b, whereby leaking of oil between the intake port 12 and the discharge port 13 can be prevented.

In the plurality of tooth shape sections 6, 6, . . . , there is a prescribed interval between the adjacent tooth shape sections 6, 6. The interval between the adjacent tooth shape sections 6, 6 is greater than the size of one of the inside position tooth shapes 6 a and outside position tooth shapes 6 b. In the present invention, the number of tooth shape sections 6 is no less than three and no more than eight. By setting the number of tooth shape sections 6 to no less than eight, it is possible to ensure that the interval between the adjacent tooth shape sections 6, 6 is no less than the size of one tooth.

The desirable number of tooth shape sections 6 is no less than three and no more than six. FIG. 5 shows the initial position and final position in an embodiment in which the number of tooth shape sections 6 is three. FIG. 6 shows the initial position and final position in an embodiment in which the number of tooth shape sections 6 is six. Furthermore, even more desirably, the number of tooth shape sections 6 is four or five.

In particular, the optimal number of tooth shape sections 6 is four (see FIG. 1 to FIG. 4). By setting the number of tooth shape sections 6 to four, as described above, it is possible to achieve, in the smoothest possible manner, both the role of accurately guiding the center of diameter Pc of the outer ring 5, in other words, the center of rotation Pb of the outer rotor 4, to move along the fan-shaped rotation trajectory Q, and the role of shutting off leakage of oil in the gap between the outer ring 5 and the rotor chamber 1 positioned between the intake port 12 and the discharge port 13. Furthermore, the number of tooth shape sections 6, which require high precision, can be reduced and therefore costs can be lowered.

In the present invention, the initial position of the inner rotor 3 and the outer rotor 4 is a position in which the initial position eccentric axis line La passes on the first sealing land 14, and the cell volume becomes largest when the cell S passes the first sealing land 14 and this cell is called the largest cell Sa. Furthermore, when the outer ring 5 swings to a maximum extent, the center of rotation Pb of the outer rotor 4 moves along the final position eccentric axis line Lx. In other words, the largest cell Sa reaches the final position eccentric axis line Lx and is also positioned over the intake port 12.

One example of the operation of the oil pump of the present invention is described here on the basis of FIG. 8. The operation of the oil pump is determined by the number of revolutions (speed) of the engine in which the oil pump is installed. Here, the speed range of the engine is divided into a low-speed range, a medium-speed range and a high-speed range. The operating means 9 which causes the outer ring 5 to swing employs a hydraulic means, and a solenoid valve is desirable for the same (see FIG. 7A).

Firstly, in the low-speed range of the engine, the outer ring 5 and the outer rotor 4 are in the initial position and the largest cell Sa passes over the first sealing land 14 (see FIG. 2). In the operating chamber 2, the operating protrusion 51 is impelled elastically by the elastic pressing section 8 in such a manner that the outer ring 5 is positioned at the initial position (see FIG. 2A, FIGS. 7A, 7B). The first oil passage 21 and the second oil passage 22 are opened by the operating means 9, and oil is sent into the operating chamber 2 from both the first oil chamber 21 and the second oil chamber 22 (see FIG. 8(B)). In this case, a force based on hydraulic pressure of substantially the same magnitude is applied to the first pressure receiving surface 51 a and the second pressure receiving surface 51 b of the operating protrusion 51.

Consequently, there is virtually no hydraulic pressure differential between the first pressure receiving surface 52 a and the second pressure receiving surface 52 b, the force of the elastic pressing section 8 is the dominant force on the operating protrusion 51, and the outer ring 5 is held in the initial position (see FIG. 2(A), FIGS. 8(A), (B)). When the outer ring 5 and the outer rotor 4 are in the initial position, the largest cell Sa is positioned on the first sealing land 14, and the discharge amount of oil per revolution due to the inner rotor 3 and the outer rotor 4 is a maximum.

When the engine is in the medium-speed range, the first oil passage 21 is opened and the second oil passage 22 is closed by the operating means. The force of the hydraulic pressure on the side of the first oil passage 21 is greater than the elastic force of the elastic pressing unit 8, and the operating protrusion 51 moves to the final position side (see FIG. 4, FIGS. 8A, 8C). Consequently, the largest cell Sa passes through the final position eccentric axis line Lx (see FIG. 4), the oil discharge amount per revolution becomes smallest, and the hydraulic pressure can be maintained at a low value.

In the region of change in the engine speed near the transition from the medium-speed range to the high-speed range, the first oil passage 21 and the second oil passage 22 are opened by the operating means 9, and oil is sent into the operating chamber 2 from both the first oil chamber 21 and the second oil chamber 22 (see FIGS. 8(A) and 8(B)). In this case, a force based on hydraulic pressure of substantially the same magnitude is applied to the first pressure receiving surface 51 a and the second pressure receiving surface 51 b of the operating protrusion 51.

Consequently, there is virtually no hydraulic pressure differential between the first pressure receiving surface 51 a and the second pressure receiving surface 51 b, the force of the elastic pressing section 8 is the dominant force on the operating protrusion 51, the outer ring 5 and the outer rotor 4 return to the initial position, and the largest cell Sa is positioned on the first sealing land 14, the oil discharge amount per revolution by the inner rotor 3 and the outer rotor 4 becomes a maximum, and the hydraulic pressure increases dramatically (see FIG. 8(A)).

When the engine is in the high-speed range, the first oil passage 21 is opened and the second oil passage 22 is closed by the operating means 9 (see FIG. 4, FIGS. 8(A), 8(C)). The force of the hydraulic pressure on the side of the first oil passage 21 is greater than the elastic force of the elastic pressing unit 8, and the operating protrusion 51 moves to the final position side. Consequently, the largest cell Sa passes through the final position eccentric axis line Lx (see FIG. 4), the oil discharge amount per revolution becomes smallest, and the hydraulic pressure can be maintained at a low value (see FIG. 4). By adopting a configuration of this kind, cooling and lubrication are ensured when the engine speed is high, excessive increase in the hydraulic pressure is avoided, and components in the oil filter and the oil circuit are prevented from suffering problems due to high hydraulic pressure.

The embodiments described above disclose the following features.

(Feature 1)

An oil pump including: an inner rotor having outer teeth; an outer rotor having inner teeth which form cells together with the outer teeth, the outer rotor rotating with a prescribed amount of eccentricity with respect to the center of rotation of the inner rotor; an outer ring which causes the center of rotation of the outer rotor to swing along a fan-shaped rotation trajectory having a radius equal to the amount of eccentricity, with respect to the center of rotation of the inner rotor; an operating means which causes a swinging movement of the outer ring; and a pump housing which has a rotor chamber having an intake port and a discharge port, the portion between a final end section of the intake port and a start end section of the discharge port being taken to be a first sealing land, and which houses the inner rotor, the outer rotor and the outer ring, wherein the oil pump is provided with no less than three and no more than eight tooth shape sections, each formed of an outside position tooth shape formed in the rotor chamber and an inside position tooth shape which is formed in the outer ring to form a pair with the outside position tooth shape and which intermeshes therewith at all times while moving, a prescribed interval is provided between the adjacent tooth shape sections, and a seal section is provided in at least one of the rotor chamber and the outer ring, the seal section abutting against the other of the rotor chamber and the outer ring, and shutting off the intake port from the discharge port.

(Feature 2)

An oil pump including: an inner rotor having outer teeth; an outer rotor having inner teeth which form cells together with the outer teeth, the outer rotor rotating with a prescribed amount of eccentricity with respect to the center of rotation of the inner rotor; an outer ring which causes the center of rotation of the outer rotor to swing along a fan-shaped rotation trajectory having a radius equal to the amount of eccentricity, with respect to the center of rotation of the inner rotor; an operating means which causes a swinging movement of the outer ring; and a pump housing which has a rotor chamber having an intake port and a discharge port, the portion between a final end section of the intake port and a start end section of the discharge port being taken to be a first sealing land, and which houses the inner rotor, the outer rotor and the outer ring, wherein the oil pump is provided with no less than three and no more than eight tooth shape sections, each formed of an outside position tooth shape formed in the rotor chamber and an inside position tooth shape which is formed in the outer ring to form a pair with the outside position tooth shape and which intermeshes therewith at all times while moving, a prescribed interval is provided between the adjacent tooth shape sections, in a low-speed range of the engine, the outer rotor is in an initial position due to the outer ring, and the cell on the first sealing land becomes largest, and in a medium-speed range and high-speed range of the engine, the cell is over the intake port and the cell becomes largest.

REFERENCE SIGNS LIST

-   A: Pump housing -   1: Rotor chamber -   12: Intake port -   13: Discharge port -   14: First sealing land -   2: Operating chamber -   21: First oil passage -   22: Second oil passage -   3: Inner rotor -   4: Outer rotor -   5: Outer ring -   51: Operating protrusion -   51 a: First pressure receiving surface -   51 b: Second pressure receiving surface -   6: Tooth shape section -   6 a: Inside position tooth shape -   6 b: Outside position tooth shape -   7: Sealing section -   8: Elastic pressing section -   9: Operating means -   e: Amount of eccentricity -   Q: Fan-shaped rotation trajectory -   Pa: Center of rotation -   Pb: Center of rotation 

1. An oil pump, comprising: an inner rotor having outer teeth; an outer rotor having inner teeth which form cells together with the outer teeth, the outer rotor rotating with a prescribed amount of eccentricity with respect to the center of rotation of the inner rotor; an outer ring which causes the center of rotation of the outer rotor to swing along a fan-shaped rotation trajectory having a radius equal to the amount of eccentricity, with respect to the center of rotation of the inner rotor; an operating means which causes a swinging movement of the outer ring; and a pump housing which has a rotor chamber having an intake port and a discharge port, the portion between a final end section of the intake port and a start end section of the discharge port being taken to be a first sealing land, and which houses the inner rotor, the outer rotor and the outer ring, wherein the oil pump is provided with no less than three and no more than eight tooth shape sections, each formed of an outside position tooth shape formed in the rotor chamber and an inside position tooth shape which is formed in the outer ring to form a pair with the outside position tooth shape and which intermeshes therewith at all times while moving, and a prescribed interval is provided between the adjacent tooth shape sections.
 2. The oil pump according to claim 1, wherein the number of tooth shape sections is no less than three and no more than six.
 3. The oil pump according to claim 1, wherein the number of tooth shape sections is four or five.
 4. The oil pump according to claim 1, wherein the number of tooth shape sections is four.
 5. The oil pump according to claim 1, wherein an operating protrusion, one side of which in a swinging direction is taken to be a first pressure receiving surface and the other side of which is taken to be a second pressure receiving surface, is formed on an outer circumference of the outer ring, an operating chamber in which the operating protrusion is accommodated swingably is formed adjacently to and in connection with the rotor chamber, a first oil passage for sending oil to the first pressure receiving surface by the operating means and a second oil passage for sending oil to the second pressure receiving surface by the operating means are formed in the operating chamber, and the operating protrusion is configured to swing due to an oil pressure differential between the first oil passage side and the second oil passage side. 